Seal element

ABSTRACT

A sealing element ( 10 ) for use in establishing a seal in an annulus ( 50 ) between a mandrel ( 52 ) and a bore wall ( 54 ) comprises an annular body ( 12 ) which defines a through bore ( 14 ) to permit mounting of the sealing element ( 10 ) on a mandrel ( 52 ), and further defines an inner surface ( 16 ), an outer surface ( 18 ) and opposing axial ends ( 20, 22 ). A pair of inner circumferential grooves ( 24, 26 ) are formed in the inner surface ( 16 ) of the annular body ( 12 ), wherein each groove ( 24, 26 ) is defined by first and second opposing ramp surfaces ( 224   a,    24   b,    26   a,    26   b ) extending from the inner surface ( 16 ) of the annular body ( 12 ), wherein the first ramp surface ( 24   a,    26   a ) defines a shallower ramp angle than the second ramp surface ( 24   b,    26   b ). The ends ( 20, 22 ) of the body ( 12 ) are configured to receive an axial setting force to axially compress the annular body ( 12 ) and cause radial expansion thereof to, in use, establish a seal between the inner surface ( 16 ) and the mandrel ( 52 ), and the outer surface ( 18 ) and a bore wall ( 54 ).

FIELD OF THE INVENTION

The present invention relates to a seal element for use in establishing a seal in an annulus, such as within a wellbore.

BACKGROUND TO THE INVENTION

Packers are commonly used in the oil and gas industry for sealing an annulus in a wellbore. The annulus might exist, for example, between a wellbore liner or casing and a production tubing extending through the liner or casing.

Known packers may comprise an elastomeric annular sealing element mounted on a mandrel and which is capable of being extended radially outwardly to engage, for example, the wall of a bore in which the packer is located, thus providing a seal in the annulus defined between the mandrel and the bore wall. The seal element may be axially compressed, for example by a setting tool, to effect radial expansion.

However, the present inventors have recognised some drawbacks associated with some conventional packers. For example, it has been recognised that annular sealing elements, when axially compressed, will tend to define an increasing inner diameter. This effect can result in a seal element moving away from a mandrel and defining a leak path therebetween, making it difficult to establish an appropriate seal between the seal element and the mandrel. To address this issue it may be necessary to apply a greater setting force, to increase the deformation and strain within the element, to effectively press or squeeze the element into the annular space. However, this increased level of strain can also set a significant level of stress within the seal element, possibly minimising the available resistance to pressure forces when in use. Furthermore, in some circumstances uncontrolled buckling of an annular element may occur, which could result in an ineffective seal.

Also, known seal elements often define a stiffness variation, for example due to connection requirements, material selection and the like. However, regions of increased stiffness may cause increased levels of stress to be experienced in these and possibly adjacent regions during setting of the element, such that the seal element may be compromised in terms of its available resistance to pressure induced stresses and ability to resist extrusion within the annulus.

SUMMARY OF THE INVENTION

According to a first aspect of the present invention there is provided a sealing element for use in establishing a seal in an annulus between a mandrel and a bore wall, comprising:

an annular body defining a through bore to permit mounting of the sealing element on a mandrel, and further defining an inner surface, an outer surface and opposing axial ends, wherein the ends are configured to receive an axial setting force to axially compress the annular body and cause radial expansion thereof to, in use, establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and

a pair of inner circumferential grooves formed in the inner surface of the annular body, wherein each groove is defined by first and second opposing ramp surfaces extending from the inner surface of the annular body, wherein the first ramp surface defines a shallower ramp angle than the second ramp surface.

In use, the annular body may be mounted on the outer surface of a mandrel, such as a pipe, tooling sleeve or the like, and the mandrel located within a bore, such as a wellbore, pipe line or the like. An axial compression force applied through the opposing axial ends of the annular body will cause the body the be axially compressed and in turn radially expanded such that the inner surface of the body establishes a seal with the mandrel, and the outer surface establishes a seal with the wall of the bore, thus sealing the annulus between the mandrel and the bore wall. The axial setting force may be applied by any means, such as via a setting tool. Also, the axial setting force may be any force which at least has a force component extending generally axially or longitudinally relative to the annular body.

The first and second ramp surfaces of each groove may extend from the inner surface towards a groove trough. Such a groove trough may define a maximum depth of the groove. The trough may be defined by a surface, such as one or more further ramp surfaces, one or more cylindrical surfaces or the like, extending between the first and second ramp surfaces. The trough may be defined at a point of connection or merging of the first and second ramp surfaces. The trough may define a radius interconnection, such as a curved intersection with a constant or varying radius, between the first and second ramp surfaces.

The grooves may effectively reduce the stiffness of the annular body such that deformation during setting induces less stress within the annular body. This arrangement may permit the sealing element, once set, to resist a greater level of stress caused by operational forces (typically derived from axial pressure forces) before approaching yield limits. That is, the proportion of the total available stress limit of the seal element which is required to accommodate stresses induced by the setting procedure are minimised. Further, the grooves may effectively reduce the stiffness of the annular body at desired locations, providing a degree of control of the behaviour of the annular body when exposed to a setting force.

As defined above, each groove includes first and second ramp surfaces, wherein the first ramp surface defines a shallower ramp angle than the second ramp surface. That is, the first ramp surface defines a ramp angle relative to a longitudinal centre axis of the annular body which is less than the corresponding ramp angle of the second surface. This arrangement therefore establishes a degree of asymmetry within each groove, with one side, specifically the first ramp surface of each groove defining a relatively shallow or gentle slope, and the other side, specifically the second ramp surface of each groove defining a relatively steep slope. The asymmetry may be defined laterally through each groove.

The first ramp surfaces may define a ramp angle of, for example, between 1 and 80 degrees. The second ramp surfaces may define a ramp angle of, for example, between 1 and 90 degrees, although angles outside these ranges are possible in some embodiments.

The form, such as the asymmetric form, of the grooves may facilitate a preferential transmission of an axial setting force through the annular body, which may provide a preferential and/or controlled deformation of the annular body during setting. In particular, the form of the circumferential grooves may permit an axial setting force to be transmitted in such a manner that the annular body is preferentially expanded both radially outwardly and inwardly, to establish effective inner and outer sealing. In this respect, the provision and particular form of the grooves may address issues known in the art in which axial compression of annular elements typically results in increasing the inner diameter, which in a sealing application can be undesirable as the seal effect with a mandrel may not be sufficiently achieved. Further, as the grooves may effectively reduce the stiffness of the annular body, any requirement to apply additional strain to effect a sufficient seal may be achieved while minimising the associated stress.

The form, and in particular the asymmetric form, of the circumferential grooves may preferentially establish a radial force component from an axial setting force in both outwardly and inwardly radial directions to preferentially cause the annular body to be extended both radially outwardly and inwardly. The asymmetry of the grooves may permit a preferential asymmetry of the established radial force components to be achieved which may provide a desired setting action of the annular body. For example, the established radial force components may permit radial expansion of desired regions of the annular body before others.

The form, and in particular the asymmetric form, of the circumferential grooves may permit an axial setting force to be transmitted in such a manner that the annular body is preferentially or controllably buckled during setting. This controlled buckling may permit improved radial expansion of the body to be achieved. In such an arrangement the annular body may be subject to a combination of bucking and material expansion upon application of an axial setting force. In some embodiments the circumferential grooves may be configured to encourage radially outward buckling of the annular element, at least during initial stages of setting of the seal element.

The form, and in particular the asymmetric form, of the circumferential grooves may preferentially affect the behaviour of the outer surface of the annular body during setting. For example, the form of the grooves may facilitate preferential radial extension of at least some portions of the outer surface of the annular body. This may involve encouraging or causing a central region of the annular body to extend radially outwardly before end regions of the body. In certain embodiments the central region of an annular body may define a region of lowest stiffness, such that causing extension or deformation to occur in this region before stiffer end regions may minimise the global stress experienced by the annular body once set. Also, in certain embodiments causing a central region of the annular body to be extended before the end regions may assist to minimise trapping of fluid during the setting process. However, in some embodiments trapping of fluid may be desired.

The first ramp surface of each groove may extend a greater axial distance than the associated second ramp surface.

The first and second ramp surfaces may extend from portions of the inner surface of the annular body which define a common inner diameter.

The grooves may be arranged in back-to-back relationship with each other. That is, the grooves may be arranged such that the respective first and second ramp surfaces are oriented in opposing directions. In one embodiment the second ramp surfaces of the grooves may be arranged in back-to-back relationship with each other. In this way, each of the first ramp surfaces may be positioned between its associated second ramp surface and an adjacent axial end region of the annular band.

In some embodiments the grooves may be arranged in the same direction.

The pair of groves may define a circumferential band therebetween. The circumferential band may define a cylindrical surface. The second ramp surface of each groove may be located adjacent the circumferential band. Accordingly, axially directed end faces of the circumferential band may be defined by the respective second ramp surfaces of the grooves. Such an arrangement may establish a preferential transmission of an axial setting force through the annular body, which may provide a preferential and/or controlled deformation of the annular body during setting. For example, such an arrangement may facilitate inward extension of the circumferential band to form a seal with a mandrel. Furthermore, arranging the grooves such that the steeper second ramp surfaces are located adjacent the circumferential band may cause the annular band to bulge radially inwardly when the annular body is exposed to an axial setting force. Such bulging may counter any tendency for the annular body, or at least portions thereof, to define an increasing inner diameter during setting.

In an alternative embodiment the first ramp surfaces may be located adjacent the circumferential band. In a further alternative embodiment the first ramp surface of one groove and the second ramp surface of the other grove may be located adjacent the circumferential band.

The circumferential band defined between the grooves may be located within a central region of the annular body, between the opposing axial ends. A lateral centre plane of the annular body may extend through the circumferential band.

The circumferential grooves may divide the inner surface of the annular body into at least first, second and third inner surface regions, wherein the second region is interposed between the grooves. In such an arrangement the second inner surface region may be provided on a circumferential band defined between the grooves, such as described above.

At least one, and in some embodiments each of the first, second and third inner surface regions may define cylindrical surfaces. Two or more of the inner surfaces may define substantially equivalent inner diameters. One or more of the first, second and third inner surface regions may define a non-cylindrical surface. For example, one inner surface region may define a tapered surface, and/or may define a region of reduced inner diameter.

The first inner surface region may extend from one axial end of the annular body. The third inner surface region may extend from an opposite axial end of the annular body. One or both of the first and third inner surface regions may extend from a region which is axially spaced from one or both axial ends.

The grooves may be arranged such that the first ramp surfaces of the grooves extend from a respective one of the first and third inner surface regions, and the second ramp surfaces extend from the intermediate second inner surface region. This arrangement may present the grooves in back-to-back relationship.

One or more of the ramp surfaces may define annular tapered surfaces, for example to define an outline of a truncated cone. One or more of the ramp surfaces may be curved, for example convex or concave.

The circumferential grooves may be configured similarly.

The circumferential grooves may be configured differently.

The sealing element may include one or more further circumferential grooves defined in the inner surface of the annular body. Such further grooves may be configured in the same manner as one or both of the pair of circumferential grooves.

The sealing element may comprise one or more relief ports extending between inner and outer surfaces of the annular body. A relief port may be provided to permit fluid communication between inner and outer surfaces, for example to permit release of fluid during setting of the seal element. A relief port may extend from at least one circumferential groove. A relief port may extend from an inner surface region, such as one of the first, second and third inner surface regions.

In some embodiments any circumferential groove may be configured to receive an insert material.

One or both of the opposing axial ends of the annular body may define an annular surface which is perpendicular relative to a longitudinal centre axis of the annular body.

One or both of the opposing axial ends of the annular body may define a tapered surface, so as to be obliquely aligned relative to a longitudinal centre axis of the annular body. Such an arrangement may provide a preferential transmission of an axial setting force into the annular body through the ends. For example, such an arrangement may establish a radial force component from an axial setting force. Furthermore, the provision of one or more tapered end surfaces may operate in synergy with the form, such as the asymmetric form, of the circumferential grooves to establish a preferential transmission of an applied axial setting force. The tapered surface may be defined by a chamfer, bevelled edge or the like.

One or both of the opposing axial ends may taper inwardly of the annular body.

One or both of the opposing axial ends may taper outwardly of the annular body.

One or both of the opposing axial ends may define a taper angel relative to a longitudinal centre axis of the annular body of between, for example, 45 and 89 degrees, for example between 65 and 75 degrees, such as around 70 degrees.

The surface of at least one axial end of the annular body may be aligned generally perpendicular relative to the first ramp surface of at least one circumferential groove. Generally perpendicular may include 90±15 degrees. This arrangement may establish a preferential transmission of an axially applied setting force through the annular body to establish a preferential setting of the seal element.

The annular body may comprise or define one or more reinforced regions. Such reinforced regions may be provided to increase the resistance to deformation in these regions. Such resistance to deformation may include resistance to an extrusion deformation of the annular body, for example which may be caused by exposure to a pressure differential when set to define a seal. In one embodiment opposing axial end regions of the annular body may be reinforced. The annular body may comprise one or more integrally formed reinforced regions. For example, such integrally formed reinforced regions may be provided by a material variation in such regions. Alternatively, or additionally, the annular body may include one or more separate components which may be arranged with the annular body to define reinforced regions.

The sealing element may comprise a circumferential spring arrangement provided in one end region of the annular body. Such a spring arrangement may define a region of reinforcement of the annular body. Such a spring arrangement may provide a biasing force on the annular body. In one embodiment such a spring arrangement may provide a radially inwardly directed biasing force, such as a radially inward hoop force. The spring arrangement may comprise an annular spring which may, for example, be mounted around the outer surface of the annular body, fully embedded within the annular body, or at least partially embedded within the annular body.

The sealing element may comprise one or more outer circumferential grooves provided in the outer surface of the annular body. Such an outer circumferential groove may be provided to, for example, reduce the stiffness of the annular body. Such an outer circumferential groove may be provided to provide a preferential deformation characteristic of the annular body. An outer circumferential groove may be configured similarly to an inner circumferential groove. In one embodiment an outer circumferential groove may be defined by opposing first and second ramp surfaces, wherein each ramp surface defines the same ramp angle. Such an arrangement may define a degree of symmetry within the outer circumferential groove. In one embodiment any outer circumferential groove may be axially offset from one or each inner circumferential groove.

One or both of the inner circumferential grooves may be free from any insert material.

One or both of the inner circumferential grooves may be configured to receive an insert material.

One or both of the inner circumferential grooves may be configured to receive an insert therein. Such an insert may function to assist with sealing. Such an insert may be provided to alter the mechanical properties of the sealing element at the mounted location. For example, an insert may be provided to prevent, resist and/or delay any deformation in the region on which the insert is located.

The insert may comprise an annular band.

The insert may comprise a wire which is wound around the annular body.

The insert material may comprise, for example, an elastomer, a plastic material, a polymer, PTFE, a metal, a composite, or the like.

One or both of the inner circumferential grooves may be configured to receive a ring insert.

In certain embodiments the seal element may comprise an insert material configured to be located within one or both of the outer circumferential grooves.

The annular body may comprise an elastomeric material, such as a rubber or the like.

The annular body may comprise a swellable material which is configured to swell upon appropriate exposure to an activating medium. Such swelling of the swellable material may contribute to setting of the seal element. The swellable material may be configured to swell upon exposure to water, hydrocarbons or the like.

The sealing element may be configured to be used in conjunction with a seal back-up assembly. The seal back-up assembly may be configured to provide support to the sealing element. The seal back-up assembly may be configured to provide axial support to the sealing element, for example to resist axial extrusion forces applied by any contained pressure. The seal back up assembly may be located adjacent one or both axial ends of the sealing element. The seal back-up assembly may be configured to be expandable to conform with any expansion of the sealing element. The seal back-up assembly may comprise one or more petal rings or the like.

In some embodiments the sealing element may be configured to permit a fluid to become trapped within one or more grooves formed in the annular body, for example inner and/or outer circumferential grooves. Such trapping may be achieved between the groove and any surface which is engaged by the seal element, such as a bore wall, mandrel or the like. Such trapped fluid may be pressurised by the seal element during setting thereof. In this manner the pressurised trapped fluid may function as a fluid pressure seal. That is, the trapped fluid may function as an effective fluid o-ring, for example.

According to a second aspect of the present invention there is provided a sealing assembly comprising a mandrel and a seal element according to the first aspect mounted on the mandrel.

The mandrel may comprise or define a pipe, a tool sleeve or the like.

According to a third aspect of the present invention there is provided a method for establishing a seal within an annulus between a mandrel and a bore wall, comprising:

locating a sealing element between a bore wall and a mandrel, wherein the sealing element comprises an annular body defining opposing axial ends, an outer surface and an inner surface which includes a pair of inner circumferential grooves each defined by first and second opposing ramp surfaces extending from the inner surface of the annular body, wherein the first ramp surface defines a shallower ramp angle than the second ramp surface; and

applying an axial compression force through the opposing axial ends of the annular body to axially compress the annular body and cause radial expansion thereof to establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall.

According to a fourth aspect of the present invention there is provided a sealing element for use in establishing a seal in an annulus between a mandrel and a bore wall, comprising:

an annular body defining a through bore to permit mounting of the sealing element on a mandrel, and further defining an inner surface, an outer surface and opposing axial ends, wherein the ends are configured to receive an axial setting force to axially compress the annular body and cause radial expansion thereof to, in use, establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and

at least one circumferential groove formed in at least one of the inner and outer surfaces of the annular body, wherein the groove is configured to trap fluid between the groove and a bore wall or mandrel during setting of the annular body, such that the trapped fluid defines a circumferential fluid seal.

According to a fifth aspect of the present invention there is provided a bore seal system comprising:

a bore wall;

a mandrel;

a seal element mounted on the mandrel and radially extended by axial compression thereof to extend between the mandrel and the bore wall, wherein the seal element defines at least one circumferential groove defining a space between the groove and one of the bore wall and the mandrel: and

a pressurised fluid trapped within the groove to define a circumferential fluid seal.

The action of setting the seal element may trap the fluid. The action of setting the seal element may pressurise the fluid.

According to a sixth aspect of the present invention there is provided a method for establishing a seal within an annulus between a bore wall and a mandrel, comprising:

locating a sealing element between a bore wall and a mandrel, wherein the sealing element comprises an annular body defining an inner surface, an outer surface and opposing axial ends, and including at least one circumferential groove formed in at least one of the inner and outer surfaces of the annular body;

applying an axial compression force through the opposing axial ends of the annular body to axially compress the annular body and cause radial expansion thereof to establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and

trapping and pressuring a fluid within the at least one circumferential groove during setting of the sealing element to provide a circumferential fluid seal.

According to a seventh aspect of the present invention there is provided a sealing element for use in establishing a seal in an annulus between a mandrel and a bore wall, comprising:

an annular body defining a through bore to permit mounting of the sealing element on a mandrel, and further defining an inner surface, an outer surface and opposing axial ends, wherein the ends are configured to receive an axial setting force to axially compress the annular body and cause radial expansion thereof to, in use, establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and

a pair of laterally asymmetric inner circumferential grooves formed in the inner surface of the annular body.

It should be understood that the features defined above in accordance with any aspect of the present invention or below in relation to any specific embodiment of the invention may be utilised, either alone or in combination, with any other defined feature, in any other aspect or embodiment of the invention.

BRIEF DESCRIPTION OF THE DRAWINGS

These and other aspects of the present invention will now be described, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a cross-sectional view of a seal element according to one embodiment of the present invention;

FIGS. 2A to 2D provide diagrammatic illustrations of a wall cross-section of the seal of FIG. 1 during different stages of being set to establish a seal between a mandrel and a bore wall;

FIG. 3 provides a diagrammatic illustration of a wall cross-section of a seal element which includes fluid seals; and

FIG. 4 provides a cross-sectional view of a seal element according to a further embodiment of the present invention, shown arranged with a sealing assembly.

DETAILED DESCRIPTION OF THE DRAWINGS

A sealing element, generally identified by reference numeral 10, according to an exemplary embodiment of the present invention is shown in cross-section in FIG. 1. The sealing element 10 in the present embodiment is intended to be used to establish a seal within an annulus, such as may be formed between a mandrel and a bore wall.

The sealing element 10 includes an annular body 12 which defines a through bore 14 to permit mounting of the sealing element on a mandrel (not shown for clarity). The sealing element 10 may be formed from an elastic material, such as an elastomer, for example rubber.

The sealing element 10 further defines an inner surface 16, an outer surface 18 and opposing axial ends 20, 22. As will be described in further detail below, in use, the ends 20, 22 receive an axial setting force, for example via a setting tool (not shown), to axially compress the annular body 12 and cause radial expansion thereof to establish a seal between the inner surface 16 and the mandrel (not shown), and the outer surface 18 and a bore wall (not shown).

The sealing element 10 further includes a pair of inner circumferential grooves 24, 26 formed in the inner surface 16 of the annular body 12 and arranged in back-to-back relationship with each other. Groove 24 is defined by first and second opposing ramp surfaces 24 a, 24 b which merge at a radiused groove trough 24 c, wherein the first ramp surface 24 a defines a shallower ramp angle than the second ramp surface 24 b. Similarly, groove 26 is defined by first and second opposing ramp surfaces 26 a, 26 b which merge at a radiused groove trough 26 c, wherein the first ramp surface 26 a defines a shallower ramp angle than the second ramp surface 26 b. That is, each first ramp surface 24 a, 26 a defines a ramp angle relative to a longitudinal centre axis 28 of the annular body 12 which is less than the corresponding ramp angle of each corresponding second surface 24 b, 26 b. This arrangement therefore establishes a degree of asymmetry within each groove, with one side, specifically the first ramp surface 24 a, 26 a of each groove 24, 26 defining a relatively shallow or gentle slope, and the other side, specifically the second ramp surface 24 b, 26 b of each groove 24, 26 defining a relatively steep slope. The asymmetry may be defined laterally through each groove 24, 26.

The first ramp surface 24 a, 26 a of each groove 24, 26 extends a greater axial distance than the associated second ramp surfaces 24 b, 26 b.

The circumferential grooves 24, 26 divide the inner surface 16 of the annular body 12 into first, second and third inner surface regions 30, 32, 34, wherein the second region 32 is interposed between the grooves 24, 26. In the present embodiment the second inner surface region 32 is provided on a circumferential band 36 defined between the grooves, wherein the respective second ramp surfaces 24 b, 26 b of each groove 24, 26 define axial end faces of this circumferential band 36. Further, the first inner surface region 30 extends from one axial end 20 of the annular body 12, and the third inner surface region 22 extends from the opposite axial end 22. Also, the first ramp surfaces 24 a, 24 b of the grooves 24, 26 extend from a respective one of the first and third inner surface regions 30, 34. This arrangement may present the grooves in back-to-back relationship.

In the present embodiment the first, second and third inner surface regions 30, 32, 34 define cylindrical surfaces of substantially equivalent inner diameter. However, in other embodiments one or more of the first, second and third inner surface regions may define a non-cylindrical surface and/or may define a variation in inner diameter.

The form of the grooves 24, 26, such as their asymmetric form, may provide particular advantages, some of which are noted below.

In use, the grooves 24, 26 may effectively reduce the stiffness of the annular body 12 such that deformation during setting induces less stress. This arrangement may permit the sealing element 10, once set, to resist a greater level of stress caused by operational forces, typically derived from axial pressure forces. Further, the grooves 24, 26 may effectively reduce the stiffness of the annular body at desired locations, providing a degree of control of the behaviour of the annular body when exposed to a setting force.

Also, the grooves 24, 26 may facilitate a preferential transmission of an axial setting force through the annular body 12, which may provide a preferential and/or controlled deformation during setting. In particular, the form of the circumferential grooves 24, 26 may permit an axial setting force to be transmitted in such a manner that the annular body 12 is preferentially expanded both radially outwardly and inwardly, to establish effective inner and outer sealing.

Further, the asymmetric form of the circumferential grooves 24, 26 may preferentially establish a radial force component from an axial setting force in both outwardly and inwardly radial directions to preferentially cause the annular body 12 to be extended both radially outwardly and inwardly. The asymmetry of the grooves 24, 26 may permit a preferential asymmetry of the established outward and inward radial force components to be achieved which may provide a desired setting action of the annular body.

Also, the asymmetric form of the circumferential grooves 24, 26 may permit an axial setting force to be transmitted in such a manner that the annular body is preferentially or controllably buckled during setting.

Furthermore, arranging the grooves 24, 26 such that the steeper second ramp surfaces 24 b, 26 b are located adjacent the circumferential band 36 may cause the band 36 to bulge radially inwardly when the annular body 12 is exposed to an axial setting force. Such bulging may counter any tendency for the annular body 12, or at least portions thereof, to define an increasing inner diameter during setting.

The annular body 12 includes a number of relief ports 38 extending between inner and outer surfaces of the annular body 12. In particular, diametrically opposed relief ports 38 extend from a respective groove 24, 26 to the outer surface 18 of the body 12 to permit release of fluid during setting of the seal element 10.

In the present embodiment the opposing axial ends 20, 22 of the annular body 12 define tapered surfaces 20 a, 22 a, each tapering inwardly relative to the body 12. Such an arrangement may provide a preferential transmission of an axial setting force into the annular body 12 through the ends 20, 22. For example, such an arrangement may establish a radial force component from an axial setting force. Also, the tapered end surfaces 20 a, 22 a operate in synergy with the circumferential grooves to establish a preferential transmission of an applied axial setting force.

In the present embodiment, the tapered end surfaces 20 a, 22 a are aligned generally perpendicular with the first ramp surface 24 a, 26 a of an adjacent circumferential groove 24, 26. Generally perpendicular may include 90±15 degrees. This arrangement may establish a preferential transmission of an axially applied setting force through the annular body 12 to establish a preferential setting of the seal element 10.

The annular body 12 comprises three axially spaced outer circumferential grooves 40, 42, 44 provided in the outer surface 18 of the body 12. These outer grooves may each be generally symmetrical in form, and may be utilised to reduce the stiffness of the annular body 12, and assist to provide a preferential deformation characteristic of the annular body 12. In the present embodiment the outer grooves 40, 42, 44 are axially staggered relative to the inner grooves 24, 26.

A circumferential spring 46, 48 is mounted on each end 20, 22 of the annular body 12. These springs 46, 48 may define regions of reinforcement of the annular body 12. Furthermore, the springs 46, 48 may provide a biasing force on the annular body 12, and in particular a radially inwardly directed biasing force, such as a radially inward hoop force.

Reference is now made to FIGS. 2A to 2D which show a cross-sectional wall portion of the sealing element 10 of FIG. 1 during different states of setting to seal an annulus 50 between a mandrel 52 and a bore wall 54. The mandrel 52 may be defined by, for example, a pipe structure, a tool sleeve or the like. The bore wall 54 may be defined by an open drilled bore, a casing, liner, pipeline or the like.

In FIG. 2A the annular body 12 is shown in a relaxed state.

In FIG. 2B an axial setting force, illustrated by arrows 56 is applied through the opposing ends 20, 22 of the body 12. The lower end 22 is held stationary, for example by abutment with a collar (not shown) mounted on the mandrel 52, while the upper end 20 is axially displaced. The setting force may be applied via a setting tool (not shown). During this initial setting stage of FIG. 2B, the asymmetric form of the inner circumferential grooves 24, 26 causes the central region of the annular body 12 to buckle radially outwardly and make initial contact with the bore wall 54. Furthermore, the asymmetric form and arrangement of the inner grooves 24, 26 cause the circumferential band 36 between the grooves 24, 26 to bulge radially inwardly, thus countering or minimising any effect of the inner diameter also increasing due to the bucking effect.

Further, as shown in FIG. 2B, the provision of the tapered ends 20 a, 22 a of the annular body 12 encourages these ends to be displaced radially outwardly. This may redirect the axial setting force to be applied more centrally of the annulus 50, which may assist in providing preferential deformation and activation of the annular body 12.

Further axial compression, as shown in FIG. 2C causes further deformation of the annular body 12 to comply with the shape of the annulus 50. As shown, during setting the inner and outer grooves 24, 26, 40, 42, 44 begin to close, and an increasing area of the inner and outer surfaces become engaged with the mandrel 52 and bore wall 54.

Continued axial compression, as shown in FIG. 2D completely sets the annular body 12 in the annulus 50, with the grooves 24, 26, 40, 42, 44 completely closed.

An alternative arrangement is illustrated in FIG. 3, which shows the sealing element 10 once again set within an annulus 50 between a mandrel 52 and a bore wall 54. In this case, however, the outer grooves 40, 42, 44 during setting of the body 12 have trapped a fluid against the bore wall 54. Such fluid may become pressurised within the grooves and preferentially act as fluid o-rings, contributing to the sealing capacity of the sealing element 10. Although in this embodiment the inner grooves 24, 26 are shown entirely closed, these may additionally or alternatively trap a fluid for sealing purposes.

A sealing element in accordance with an alternative embodiment of the present invention is shown in FIG. 4, reference to which is now made. The sealing element, in this case generally identified by reference numeral 110 and shown in cross-section, is similar to the sealing element 10 first shown in FIG. 1 and as such like features share like reference numerals, incremented by 100. Accordingly, the sealing element 110 includes an annular body 112 having opposing ends 120, 122 and which includes a pair of inner asymmetric circumferential grooves 124, 126 formed in its inner surface 116. In the present embodiment the annular body 112 also includes relief ports 138. However, in this case the relief ports do not extend into the grooves 124, 126, but instead open directly into the inner surface 116. Further, in the present embodiment the annular body 112 only includes a single outer groove 142 formed in its outer surface 112, and arranged axially between the inner grooves 124, 126.

An insert ring 60 may be positioned in any one of the grooves 124, 126, 142. Such a ring may be provided to assist with creating a seal. Such a ring may be provided to locally modify the mechanical properties of the sealing element 10 at the location of the ring. For example, the insert ring 60 may function to resist and/or delay outward and/or inward expansion of the annular body 112. In the specific illustrated embodiment the ring 60 is mounted within inner groove 126. The ring may be formed from any suitable material, such a metal, plastic, polymer, elastomer, PTFE or the like. The insert ring may be provided in any form, such as by a continuous ring or band, by wrapping a wire into the associated groove or the like. It should be understood that the disclosed insert ring 60 is not limited only for use within the current embodiment, and may be used in any annular sealing element which includes a groove.

In the FIG. 4 the sealing element 110 is shown in combination with opposing back-up assemblies 62, 64, arranged adjacent the opposing ends 120, 124 of the annular body 112. Each back-up assembly includes a back-up structure 66, 68 which captivates the end regions of the sealing element 110, and functions to provide support to these ends at least when the sealing element 110 is expanded and set. In particular, the back-up structures 66, 68 function to restrict or minimise extrusion of the sealing element 110 along an annulus due to any differential pressure to which it is exposed.

It should be understood that the embodiments described herein are merely exemplary and that various modifications may be made thereto without departing from the scope of the present invention. For example, any number of inner and/or outer grooves may be utilised. Further, the sealing element may be formed from any suitable material. In some embodiments the sealing element may include a swellable material which is induced to swell, for example upon contact with water or hydrocarbons, to assist in sealing. 

1. A sealing element for use in establishing a seal in an annulus between a mandrel and a bore wall, comprising: an annular body defining a through bore to permit mounting of the sealing element on a mandrel, and further defining an inner surface, an outer surface and opposing axial ends, wherein the ends are configured to receive an axial setting force to axially compress the annular body and cause radial expansion thereof to, in use, establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and a pair of inner circumferential grooves formed in the inner surface of the annular body, wherein each groove is defined by first and second opposing ramp surfaces extending from the inner surface of the annular body, wherein the first ramp surface defines a shallower ramp angle than the second ramp surface.
 2. The sealing element according to claim 1, wherein at least one of: the first and second ramp surfaces of each groove extend from the inner surface towards a groove trough; the first ramp surface defines a ramp angle relative to a longitudinal centre axis of the annular body which is less than the corresponding ramp angle of the second surface; the difference in ramp angles of the first and second opposing ramp surfaces defines a lateral asymmetry within each groove.
 3. (canceled)
 4. (canceled)
 5. The sealing element according to claim 1, wherein at least one of: the form of the grooves facilitates a preferential transmission of an axial setting force through the annular body; the form of the circumferential grooves permits an axial setting force to be transmitted in such a manner that the annular body is preferentially expanded both radially outwardly and inwardly; the form of the circumferential grooves preferentially establishes a radial force component from an axial setting force in both outwardly and inwardly radial directions to preferentially cause the annular body to be extended both radially outwardly and inwardly; the form of the grooves permits a preferential asymmetry of the established radial force components to be achieved.
 6. (canceled)
 7. (canceled)
 8. (canceled)
 9. The sealing element according to claim 1, wherein at least one of: the form of the circumferential grooves permits an axial setting force to be transmitted in such a manner that the annular body is controllably buckled during setting; the annular body is configured to be subject to a combination of bucking and material expansion upon application of an axial setting force.
 10. (canceled)
 11. (canceled)
 12. The sealing element according to claim 1, wherein at least one of: the form of the circumferential grooves encourage a central region of the annular body to extend radially outwardly before end regions of the body; the first ramp surface of each groove extends a greater axial distance than the associated second ramp surface; the first and second ramp surfaces extend from portions of the inner surface of the annular body which define a common inner diameter.
 13. (canceled)
 14. (canceled)
 15. The sealing element according to claim 1, wherein at least one of: the grooves are arranged in back-to-back relationship with each other; the second ramp surfaces of the grooves are arranged in back-to-back relationship with each other.
 16. (canceled)
 17. The sealing element according to claim 1, wherein at least one of: the pair of circumferential groves define a circumferential band therebetween; the second ramp surface of each groove are located adjacent the circumferential band; axially directed end faces of the circumferential band are defined by the respective second ramp surfaces of the grooves; the form of the grooves cause the circumferential band to bulge radially inwardly when the annular body is exposed to an axial setting force; the circumferential band is located within a central region of the annular body, between the opposing axial ends.
 18. (canceled)
 19. (canceled)
 20. (canceled)
 21. (canceled)
 22. The sealing element according to claim 17, wherein the circumferential grooves divide the inner surface of the annular body into at least first, second and third inner surface regions, wherein the second region is interposed between the grooves, the second inner surface region being provided on the circumferential band defined between the grooves.
 23. The sealing element according to claim 22, wherein at least one of: at least one of the first, second and third inner surface regions define cylindrical surfaces; two or more of the first, second and third inner surface regions define substantially equivalent inner diameters; the first inner surface region extends from one axial end of the annular body; the first inner surface region extends from one axial end of the annular body; the third inner surface region extends from an opposite axial end of the annular body; the grooves are arranged such that the first ramp surfaces of the grooves extend from a respective one of the first and third inner surface regions, and the second ramp surfaces extend from the intermediate second inner surface region.
 24. (canceled)
 25. (canceled)
 26. (canceled)
 27. (canceled)
 28. The sealing element according to claim 1, comprising one or more further circumferential grooves defined in the inner surface of the annular body.
 29. The sealing element according to claim 1, wherein at least one of: the sealing element comprises one or more relief ports extending between inner and outer surfaces of the annular body to permit fluid communication between inner and outer surfaces and allow release of fluid during setting of the seal element; a relief port extends from at least one circumferential groove; a relief port extends from an inner surface region of the body which is outside the grooves.
 30. (canceled)
 31. (canceled)
 32. The sealing element according to claim 1, wherein at least one of: at least one of the opposing axial ends of the annular body define an annular surface which is perpendicular relative to a longitudinal centre axis of the annular body; at least one of the opposing axial ends of the annular body define a tapered surface, so as to be obliquely aligned relative to a longitudinal centre axis of the annular body; at least one of the opposing axial ends of the annular body define a tapered surface, so as to be obliquely aligned relative to a longitudinal centre axis of the annular body, the tapered surface providing a preferential transmission of an axial setting force into the annular body through the ends; at least one of the opposing axial ends of the annular body taper inwardly of the annular body; the surface of at least one axial end of the annular body is aligned generally perpendicular relative to the first ramp surface of at least one circumferential groove.
 33. (canceled)
 34. (canceled)
 35. (canceled)
 36. (canceled)
 37. The sealing element according to claim 1, wherein at least one of: the annular body comprises or defines one or more reinforced regions; the annular body comprises one or more integrally formed reinforced regions; the annular body includes one or more separate components which are arranged with the annular body to define reinforced regions.
 38. (canceled)
 39. (canceled)
 40. The sealing element according to claim 1, comprising a circumferential spring arrangement provided in one end region of the annular body.
 41. The sealing element according to claim 1, wherein at least one of: the sealing element comprises one or more outer circumferential grooves provided in the outer surface of the annular body; any outer circumferential groove is axially offset from one or each inner circumferential groove.
 42. (canceled)
 43. The sealing element according to claim 1, wherein at least one of: at least one of the inner circumferential grooves are free from any insert material; at least one of the inner circumferential grooves receive an insert material.
 44. (canceled)
 45. The sealing element according to claim 1, wherein the annular body comprises an elastomeric material.
 46. The sealing element according to claim 1, wherein the annular body comprises a swellable material which is configured to swell upon appropriate exposure to an activating medium.
 47. The sealing element according to claim 1, configured for use with a seal back-up assembly for providing support to the sealing element.
 48. The sealing element according to claim 1, wherein at least one groove of the annular body is configured to permit a fluid to become trapped therein to define a fluid pressure seal.
 49. A sealing assembly comprising a mandrel and a seal element according to claim 1 mounted on the mandrel.
 50. A method for establishing a seal within an annulus between a mandrel and a bore wall, comprising: locating a sealing element between a bore wall and a mandrel, wherein the sealing element comprises an annular body defining opposing axial ends, an outer surface and an inner surface which includes a pair of inner circumferential grooves each defined by first and second opposing ramp surfaces extending from the inner surface of the annular body, wherein the first ramp surface defines a shallower ramp angle than the second ramp surface; and applying an axial compression force through the opposing axial ends of the annular body to axially compress the annular body and cause radial expansion thereof to establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall.
 51. A sealing element for use in establishing a seal in an annulus between a mandrel and a bore wall, comprising: an annular body defining a through bore to permit mounting of the sealing element on a mandrel, and further defining an inner surface, an outer surface and opposing axial ends, wherein the ends are configured to receive an axial setting force to axially compress the annular body and cause radial expansion thereof to, in use, establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and at least one circumferential groove formed in at least one of the inner and outer surfaces of the annular body, wherein the groove is configured to trap fluid between the groove and a bore wall or mandrel during setting of the annular body, such that the trapped fluid defines a circumferential fluid seal.
 52. A bore seal system comprising: a bore wall; a mandrel; a seal element mounted on the mandrel and radially extended by axial compression thereof to extend between the mandrel and the bore wall, wherein the seal element defines at least one circumferential groove defining a space between the groove and one of the bore wall and the mandrel: and a pressurised fluid trapped within the groove to define a circumferential fluid seal.
 53. A method for establishing a seal within an annulus between a bore wall and a mandrel, comprising: locating a sealing element between a bore wall and a mandrel, wherein the sealing element comprises an annular body defining an inner surface, an outer surface and opposing axial ends, and including at least one circumferential groove formed in at least one of the inner and outer surfaces of the annular body; applying an axial compression force through the opposing axial ends of the annular body to axially compress the annular body and cause radial expansion thereof to establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and trapping and pressuring a fluid within the at least one circumferential groove during setting of the sealing element to provide a circumferential fluid seal.
 54. A sealing element for use in establishing a seal in an annulus between a mandrel and a bore wall, comprising: an annular body defining a through bore to permit mounting of the sealing element on a mandrel, and further defining an inner surface, an outer surface and opposing axial ends, wherein the ends are configured to receive an axial setting force to axially compress the annular body and cause radial expansion thereof to, in use, establish a seal between the inner surface and the mandrel, and the outer surface and a bore wall; and a pair of laterally asymmetric inner circumferential grooves formed in the inner surface of the annular body.
 55. (canceled)
 56. (canceled)
 57. (canceled) 